Cooler for heat removal on a semi-conductor cell built into a container



May 3, 1960 United States Patent COOLER FOR HEAT REMOVAL ON A SEMI-CON- DUCTOR CELL BUILT INTO A CONTAINER Otto Schiirli, Baden, Switzerland, assignor to Aktiengesellschaft Brown, Boveri & Cie., Baden, Switzerland, a joint-stock company Application June 10, 1957, Serial No. 664,723

Claims priority, application Switzerland June 29, 1956 2 Claims. (Cl. 317-234) This invention relates to semi-conductor cells, and is particularly concerned with the provision of means for dissipating heat from a semi-conductor cell built into a container.

In current-loaded semi-conductor cells, for example, germanium rectifier cells, it is very important that the generated heat be removed intensively from a copper plate which forms the bottom of the container. Such high capacity coolers are known per se. In the serial production of these coolers it is highly desirable that the coolers be constructed according to a simple and inexpensive mode of execution. These demands are fulfilled in a particularly advantageous manner according to the present invention.

The invention concerns a cooler for the removal of heat from a semi-conductor cell built into a container which comprises a metallic wall for the removal of heat from the container. The invention consists in that a cooling body is soldered (or otherwise is secured in heat-conductive relation) to the wall area lying outside the container, which body consists essentially of a base plate and, projecting therefrom, a plurality of cooling wings provided with elongated depressions, these depressions being arranged alternately slanting in such away that they are arranged obliquely in opposite directions and side by side from one cooling wing to the next.

The invention is explained in more detail on the basis of an illustrative example in connection with the appended drawing in which Fig. 1 is a side elevational view of a form of construction embodying principles of the invention;

Fig. 2 is a front view of one of the appended wings of the cooler, showing the arrangement of the depressions therein, and indicating in dotted lines the relationship thereto of the depressions in the adjacent wing of the cooler; and

Fig. 3 is a generally diagrammatic side elevational view with certain parts in phantom illustrating the elastic means for lifting the container from the cooler upon melting of the temperature-responsive solder connection.

In Figure 1, 1 designates a container in which a semiconductor cell 2 is disposed and to which said cell is soldered together with the metallic wall 3. The metallic wall itself preferably is composed, for example, of the vacuum enclosure 3a, consisting of Kovar and a copper disk 3b soldered on with hard solder. This metallic wall is exposed to the heating by the semi-conductor cell 2 lying closely adjacent and it therefore requires an intense cooling in order to avoid exceeding a maximum temperature. By the expression Kovar I mean an alloy, sold by Westinghouse Electric 00., having approximately the same softening temperature coefiicient as that of glass.

. 2 vprints, 7, 7, in the form of pressed-in depressions. Figure 2 shows a cooling wing with the depressions 7 placed obliquely. The adjacent wings likewise exhibit like depressions, the'direc'tions of which are, however, opposite to those of the first-mentioned wing, so that the depressions are crosswise relative to each other.

Cooling airstreaming in laterally is blown, from a source (not shown) of air under pressure, against the cooling wings. The depressions effect an intense whirling of the cooling air, approximately corresponding to the arrows, through which a very intense heat transfer again occurs from the cooling surfaces to the air. The turbulency of the air results in a cooling power of 0.5-1 kw., expressed as a weight per unit power of a cooler of 1 kg. Thus the flow of cooling air requires only a pressure equal to a 20 mm. column of water above atmospheric pressure to achieve the necessary cooling. The resulting temperature difference between the entering air and the hottest place of the cooler, namely at the base plate, amounts to about 20 degrees C. This slight temperature drop makes possible above all the intense cooling of the very temperature-sensitive germanium rectifier cells.

A further advantage of these coolers consists in this simple structure and simple form of construction. The cooling wings can be prepared from a continuous hand without waste; they can be produced including the depressions by stamping, and therefore very cheaply. If desired the wings may beplaced adjacent each other for simultaneous soldering to the base plate.

The cooler in its simple prismatic form can be used as a supporting construction part and be assembled as such with additional coolers and rectifier cells soldered on them into a larger structural unit. The rectifier is soldered on the cooling aggregate as an additional part. For the soldering there can be used a solder whose melting point lies below the highest permissible operating temperature. In this way an additional over-load protection can be attained, in that by using a supplemental elastic support for the container of the semi-conductor cell, the container may be lifted from the cooler as soon as the solder melts. In this way an automatic current interruption in thermal overload is attained. As shown in Fig. 3, the container 1 is soldered to the base plate 5 which in turn supports the cooling wings 6. Base plate 5 is secured to the rigid supporting frame. The container unit is connected to the elastic spring element 10 which is also connected to the rigid support and normally tends to bias the container unit upwardly. When the temperatureresponsive solder melts, the container unit is released and is displaced upwardly by the spring 10. If one electrical terminal should include the base plate 5, then it will be apparent that the electrical circuit to the rectifier cell will be broken when the container is moved upwardly relative to the base plate by the spring 10.

The temperature-responsive solder connection between the container 1 and the base plate 5 has been identified by the reference numeral 11.

I claim:

1. Means for cooling a metallic container having a semiconductor cell therein and secured to the bottom wall thereof, comprising a horizontal base plate secured to the external lower surface of said container, and a plurality of spaced vertical cooling wings secured at their upper ends to the lower surface of said base plate, said cooling wings having a plurality of obliquely arranged depressions therein, said cooling wings being substantially parallel and arranged with the depressions in one wing alternately slanting with respect to the depressions in the next adjacent wing whereby said depressions etfect 3 a whirling action to the cooling air passing between said References Cited in the file of this patent wings to achieve efiective heat transfer from said base UNITED STATES PATENTS plate. 2. Apparatus as defined in claim 1 wherein said base 2 53, et 2s plate is soldered to the container bottom surface by 5 2:763:822 Frola 1956 means of temperature-responsive soldered connections which will be automatically broken upon the occurrence FOREIGN PATENTS of temperature overload. 521,285 Great Britain May 16, 1940 

